An investigation into the policing of a violent pro-hunting rally outside parliament will today urge police to consider new methods to combat riots.

The recommendation follows an analysis by the Independent Police Complaints Commission of dozens of cases in which protesters sustained serious head injuries, apparently after being struck by police batons during a Countryside Alliance demonstration in September 2004. The report also criticises police for concealing their identification numbers and failing to forensically examine bloodied batons.

The demonstration, staged to coincide with the second reading of the bill to ban hunting with dogs, exposed security flaws in the House of Commons after eight hunters stormed the parliament floor.

As part of its investigations into the clashes, the IPCC passed several cases of alleged assault to the Crown Prosecution Service. Three Metropolitan police officers were tried under assault charges on the basis of television footage and witness statements. All three were acquitted.

The skirmishes in September 2004 began shortly after a folk singer told a crowd of 20,000 demonstrators: "Fight, fight for your rights, the war has begun." A few protesters tried to remove barriers in front of the parliament in an attempt to break the police lines and enter the House of Commons. Confrontations between the lines quickly escalated into scenes reminiscent of the 1980s miners strikes, with police in riot gear pitted against demonstrators hurling missiles.

The report says the event was "at times extremely violent" and it was not surprising officers had used force. "They were entitled to use force to protect themselves ... or to prevent protesters from invading parliament." But it makes a series of recommendations, including the suggestion that the use of truncheons to beat back protesters should be reviewed. Although the IPCC acknowledges that there were limited alternative options at the demonstration - water cannons were not available - it says: "It is important that tactical options other than sheer physical force, with inherent dangers, be explored as a matter of urgency ... The use of batons carries significant risk of serious injury, particularly to the head."

The report also raises concerns that the police ignored instructions to display their identification numbers, and reveals that not a single baton was subjected to forensic examination, even though "it must have been obvious" that the bloodied weapons has caused serious head injuries.

The Countryside Alliance said the report failed to ask why police were put in a position where they felt they had to use force.

A Scotland Yard spokeswoman said the force would look closely at all recommendations, but added: "All Metropolitan Police Service officers were cleared in relation to the Countryside Alliance demonstration."